Win 10 And Outlook Email

[Prudie]

I'm not expecting a definitive answer here but can't be the only one on Win 10 who uses the full MS Outlook 16 for email. This is my problem:
New email only stays bold for a very short time if at all without being opened or read. I can wake up in the morning and have 6 new emails and they are all already not bold. In settings I have only mark as read when viewed in the reading pane but have tried several combinations in that options box and nothing works.
I've trawled the net, asked real IT gurus at work and no-one has a solution that works.
It's such a basic requirement someone must know?

[Buenchico]

Is there any other device that your email is synced to? One known cause of the problem with IMAP mail is that another device accesses the mail (perhaps because it's configured to check your mail at periodic intervals) and Outlook thinks that it's been read elsewhere.

[Prudie]

Well yes it goes to my phone and a tablet but I won't have looked at them there first. It did before I moved to new laptop, win 10 and Office 2016 (from 7 and 2010) but never an issue then.
A new email will come in as I sit on my laptop and without moving from chair and without reading it the bold is gone within a couple of minutes.